State demographer: Jefferson County population has slowed since 2020 and will age further

Nancy Gideon, Estimates Demographer at the Colorado State Demography Office, told Jefferson County commissioners on Oct. 14 that the county’s population growth has slowed since about 2020 and is shifting toward an older age profile.

Gideon said Colorado’s overall growth is also slowing and that counties along the Front Range, including Jefferson County, have moved from rapid expansion to a more modest outlook. “Colorado has been one of the fastest growing states in the country for a long time, and many of the counties in the front range have been fastest growing as well. But that's changing,” she said.

The nut graf: the demographer’s projected shift matters because fewer births, more deaths and changes in migration alter labor supply, school enrollments, housing demand and local tax bases. Gideon said the state’s forecasts rely on a cohort-component model that aligns labor supply (age structure, births and deaths) with labor-demand forecasts (job growth). When labor demand does not match local supply, net migration is the balancing factor in the model.

Key findings Gideon presented for Jefferson County: - Population: Jefferson County experienced its largest growth in the 1970s; data presented by Gideon show stagnation or modest decline in total population since 2020. - Age structure: Large cohorts who moved to the county in earlier decades have aged in place, producing a strong concentration of residents in their 60s and 70s and a smaller share of children than in prior decades. - Births and deaths: Births in Jefferson County peaked in earlier decades and have been declining; absolute numbers of deaths have been rising as the population ages. Gideon emphasized these are absolute counts rather than rates. - Migration by age: Colorado and Jefferson County have historically attracted adults aged about 25–34; that pattern creates a lagged increase in births in decades that follow strong migration waves. Gideon said Jefferson County shows mild out-migration among 20‑year‑olds and modest in-migration among people in their 30s in some periods.

Gideon also explained how the office ties population projections to the economy: forecasts use job growth to estimate labor demand and then project net migration needed to match labor supply. “When our unemployment rate is lower compared to other places, we do tend to see more net migration,” she said.

On implications, Gideon said Jefferson County can expect pressure from an aging population on government budgets and services, and that the fastest-growing older cohort over the next decades is likely to be the 75-and-older group. She noted that most older residents age in place and that 82% of people 65 and over are homeowners, which can complicate efforts to free housing stock for younger households. She warned that some national disruptions — notably the COVID pandemic and changes in international migration — have made short-term trends more volatile and that the State Demography Office planned to release a revised forecast in early November.

The presentation was followed by questions from commissioners and staff about local migration patterns, the effects of remote work on commuting and labor-supply data sources. Gideon said the office uses a range of administrative sources including IRS and Social Security records and tools like OnTheMap to map where people live and where they work. She offered to provide follow-up data to county staff and commissioners.

Ending: The State Demography Office presentation ran about 45 minutes and commissioners said they would use the office’s forthcoming updated forecasts in upcoming planning discussions, including a scheduled presentation to the Jefferson County School District about school-age population trends.